Imagine a group of Homo erectus, the earliest members of our family genus, living near a coastline on an Indonesia island and well aware of a lush island that is visible only a few miles offshore. One day while on the coast, a herd of elephants emerges from the nearby forest and crosses the beach. They enter the ocean and swim successfully to the offshore island. Could this be the experience that triggers a creative process in our ancestors who are watching nearby? Does their imagination and thinking include not only a desire to reach that island, but ideas about how to do so? Could this period of creative thought conclude with the invention of a raft large enough to hold several people, food and water? If we can find evidence of this situation in the dim past, in the early days of Homo erectus, then archeologists are fixing the time and place for one of the extraordinary events in all human history, a major advance in the evolution of the human mind.

Elephants are by far the strongest large mammal, marine colonizers. They are long distant swimmers and have been observed crossing large bodies of both fresh and salt water. Herds of contemporary elephants have swum for 48 hours across large African lakes. Elephants have swum in the ocean to a distance of 48 km, sometimes reaching a speed of 2.7 km/h. Elephants frequently swim to offshore islands in India. When swimming long distances, individuals sometimes tow others who need to rest. Trunks are very well designed for the breathing challenge, and a herd can provide a founding population with breeding potential. Several elephant species crossed to the Indonesia islands east of Java, and the Philippines, where they continued to evolve and dwarf species evolved.

In 1947, the Norwegian adventurer Thor Hyerdahl’s Kon Tiki Expedition sailed a large balsa raft of Andean or South American design westward across the Pacific for 101 days. The raft was designed and built by indigenous ship builders whose people still live around Lake Titicaca, high in the Andes. Thor Hyderdahl’s theory about ancient South American journeys to Polynesia was initially controversial, but the book about the expedition was an immediate best seller and the documentary film won an Academy Award. The world was now aware that indigenous peoples and ancient civilizations could build large rafts that could undertake long, purposeful, open ocean voyages. In 2006, Thor Heyerdahl’s grandson, Olav Heyerdahl, was on the crew of the Tangaroa (named after the great Maori God of the Sea), whose journey across the Pacific honored the great Thor Heyerdahl.

Millennia before the earliest dated remains of watercraft, Homo erectus was on the move, traveling vast distances north to the Mediterranean region and then thousands of miles to the east and Asia. There is no direct archeological evidence that H. erectus ventured out upon the ocean, but the circumstantial argument that they did so with log rafts is very strong and the implications are very important. If you wanted to reach an offshore island, then either you built a large raft or boat, or indulged in extreme long distance swimming. Maybe this premise is simplistic and uncontroversial, but discussing it in detail has only recently been possible. The majority of H. erectus sites are very difficult to date with precision, and evidence for H. erectus in localities that have always been islands has only recently been discovered. The capacity to cross water to the opposite shore represents a major milestone in human history.

Robert G. Bednarik and the First Mariners Project of the International Institute of Replicative Archaeology in Australia have conducted exceptional research to find the earliest mariners. Bednarik studies H.erectus in Indonesia and the origins of marine navigation. He has published widely in both peer reviewed academic journals and venues aimed at the general public.

H.erectus has long been known in Indonesia on the island of Java, with earliest fossils dating to 1.51-1.10 million years ago. H. erectus could walk to Java on the Sunda Shelf, that now submerged continental land mass that connected the Malay Peninsula, Kalimantan, Borneo, Sumatra and Java with broad valleys. Sundaland, which is an extension of continental Asia, and the Sunda Continental Shelf did not extend further east than Java. When lower sea levels allowed Sunda to be dry land over a vast area, Australia and New Guinea were also joined by a large shallow land bridge to form the continental land mass known as Sahul.

Nonetheless, areas of open ocean remained between the eastern edge of Sunda and the western edge of Australasia throughout the late Pliocene and Pleistocene. Typical Southeast Asian wildlife does not extend beyond the Wallace Line. The Lesser Sunda Islands had distinctive animals that included both full size and dwarf elephants. In these waters there are islands that were always surrounded by ocean during the time period of H. erectus. If there is evidence for H. erectus on these ocean islands more than 500,000 years ago, then we have found history’s earliest mariners.

The Wallace Line marks the edge of the Asian and Sunda continental shelf. It lies between the islands of Nusa Tenggara (Lesser Sunda Islands) such as Borneo, Sulawesi (Celebes), Bali and Lombok. This natural boundary was first noticed by Alfred Russel Wallace, a British Naturalist who conceived a Theory of Evolution coincident with that of Charles Darwin. Considering that the water distance between Bali and Lombok is only 35 km, the ‘hardness’ of the Wallace Line is impressive.

Wallacea encompasses the islands between Sundaland (the Malay Peninsula, Sumatra, Borneo, Java, and Bali) and Near Oceania (Australia and New Guinea). These islands were always surrounded by deep water and could never be reached via a land route even when sea levels lowered during cold/glacial periods. These are the islands that required H. erectus to build rafts or boats in order to explore and settle them. The line dividing Wallacea from Australia–New Guinea is called Lydekker’s Line. Near Oceania is comprised of Australia, Tasmania, the Aru Islands, New Guinea and the Solomon Islands. At times during the Pleistocene, sea level in this region was 130 meters lower than at present and the component islands of New Oceania were joined as dry land to form the continent known as Sahul.

The islands of Wallacea, however, were never joined during these coldest intervals in the Pleistocene. Therein lies their important bio-geographical distinctiveness and the challenge to H. erectus. The animal life of these islands was, and still is, less diverse than those to their west. The islands of Wallacea have few land mammals, land birds, or freshwater fish from continental Asia because of the barrier presented by an open ocean journey. Almost half of the terrestrial vertebrates of Wallacea were endemic (i.e found nowhere else). And Wallacea was originally almost completely covered in a moist, broad leaf forest with great numbers of endemic plant species.

On the islands of Wallacea is evidence that confirmed H. erectus as the First Mariners, a milestone in human history. We can assume that the first potential seafarers were fascinated by islands easily visible and just offshore. Curiosity is always present in human consciousness. What is out there? Food? Danger? (Contact with an island out of sight cannot be documented until the Upper Pleistocene and human migration to Australasia.)

H. erectus builds the first raft and travels to the island of Flores in Wallacea

Long before the breakthrough event of travel to an island, H. erectus not only watched the occasional elephant herd swim to an offshore island, but was likely exploring offshore fishing from small rafts. The archeological record strongly implies that the ‘invention’ of a larger, seaworthy raft would be an almost routine extension of the intellectual capacities of H.erectus already in daily use.

It is very unlikely that the earliest watercraft to venture upon the sea were dugout canoes. There is no solid evidence for domesticated fire during the time period of earliest archeological evidence for H. erectus on the islands of Wallacea. It is near impossible to hollow out a tree trunk for a dugout canoe without the use of fire. The oldest known dugout canoe comes from the Netherlands, and dates to 8,600 B.C. By Mesolithic times, modern H.sapiens had dominated the planet for tens of thousands of years. H. erectus had evolved into our immediate ancestors, and thereby to extinction, before the Upper Pleistocene and the last ice age began about 110,000 BP.

We can conclude that the earliest ocean watercraft were rafts built from logs lashed together with rope made from tough plant fibers and/or palm fronds. Bamboo was plentiful in Wallacea at this time, and perhaps some driftwood logs washing up on the beach were straight and not badly rotted or cracked enough to be useful as supplemental timbers. Well then, what is the evidence that H.erectus was the first hominid to travel upon the sea? We do not have remnants of their ocean craft. Rafts built from logs lashed together would be near impossible to identify in the archeological record. Abandoned when repair is no longer possible, or wrecked upon the sea, a raft will come apart and soon cannot be identified as a human mediated ‘construction’. Perhaps a finally made paddle could be so identified but none have been found from this remote epoch.

The Sunda Shelf was not continuously exposed and easy-to-traverse forested land throughout the Middle Pleistocene (0.78-0.13 mya). That situation existed only when sea levels were at their lowest. Sumatra, Java, Bali and Kalimantan were periodically reachable by land bridges, and ocean voyaging was not required to settle them. Earliest H. erectus in Indonesia was first on Java and has been dated to 1.51-1.02 million years ago. Offshore fishing stocks must have been quickly discovered and valued, and we can surmise that brief fishing trips were a priority.

Evolving maritime navigation ability led to the crossing of 30 km of water and the colonization of the Island of Flores by 840,000 BP (late Lower Pleistocene). This settlement voyage implies the earlier colonization of Lombok and Sumbawa, the two major islands between Bali and Flores. Even at times when the sea level was at its lowest, two sea crossings were required to reach the island of Flores. First, the channel between Bali and Lombok had to be crossed, then the 9 km distance between Sumbawa and Flores had to be traversed. The crossing of the Lombok Strait may have been the first journey in history to cross ocean water with the objective to settle a new island or territory.

The island of Flores is midway between Sunda and Sahul and it was the first target for settlement by early H. erectus in the region. The Soa Basin occupies a large interior region on the island of Flores. It is about 20 km x 10 km and surrounded by mountains and active volcanoes. Throughout much of its history it was a large lake. At times, river outlets would form, the lake would drain and the Soa Basin became a grassland savannah. There is one river outlet still present. Archeologists find fossils and stone tools in tuffaceous sediments that formed in the Soa Basin during ‘dry’ periods.

Fossil deposits in the volcanic strata of the Soa Basin of Flores have many remains of the Stegdon elephant and there are typical Lower Paleolithic, human made tools in the Ola Bula Formation, central Flores. At the Mata Menge site, 19 paleomagnetic samples produced age estimates for the sediment bearing tools of 780,000 BP. Fission track analysis of the same sediments produced an age of ~800,000-720,000 BP. Earlier deposits dated to 850,000 to 920,000 BP did not contain any artifacts (Period 1). Period 3 refers to fossils and stone tools deposited at Mata Menge and five other localities between 800,000 BP and 700,000 BP. Case is closed! H. erectus as the First Mariner, rafted to the Wallacea island of Flores more than 3/4 million years ago!

Stone tools similar to those on Flores have been found on other deep water islands in Wallacea: central Timor, western Timor, Roti and Sulawesi. The finds from Timor and Roti have been identified in Middle Pleistocene deposits. Stegadons have been identified at Atambua, West Timor in six sites of the Weaiwe Formation. A Stegodont bone fragment found at To’os had been smashed and also had been laying in a fire, perhaps deliberately placed there. (But then, who or what started that fire?).

Stegodonts and H. erectus were living side by side on Timor. Although, there is no solid evidence that humans hunted Stegadonts, they could scavenge the occasional carcass. Stone tools have been found at at least six Stegodont sites, but this could indicate the preparation of carcasses, and not active hunting. Indonesian H. erectus eventually journeyed from Alor to Timor, a distance of 60 to 100 km of open water.

Humankind had launched itself upon the sea, long before we – ‘modern humans’ – had appeared on Earth. The implications for the evolution of our brain and intellectual capacity are staggering! The second article in this series will explore the extraordinary cognitive and behavioral capacities of the human mind that the first mariner journeys reveal to us.

‘Pleistocene’ refers to geology and age. ‘Paleolithic’ refers to culture. There are Lower (1.8-0.78 mya), Middle (0.78-0.13 mya) and Upper Pleistocene (0.12-0.01 mya) periods and they do not exactly overlap with Lower, Middle and Upper Paleolithic culture periods. Furthermore, each culture had a different time span on different continents. For example, Lower Paleolithic tools, which are usually viewed as somewhat crude and basic in design, persisted in some parts of Asia throughout the last ice age (Upper Pleistocene geological era). In Europe, the Lower Paleolithic approach to stone tool making disappeared everywhere as the last ice age (Upper Pleistocene) began. Furthermore, the persistence of Lower Paleolithic tool making into the Upper Pleistocene in some areas does not imply the persistence of our ancestor Homo erectus, history’s first seafarer.